Brushless DC motor configuration for a power tool

ABSTRACT

A power tool with a combined printed circuit board (PCB) having a doughnut shape and located coaxially with a motor shaft. The combined PCB is secured to a heat sink on one end of the motor and a metal end piece is positioned on an opposite end of the motor. The metal end cap and heat sink are secured to one another via fasteners to provide a rigid coupling. A tabbed end piece is provided between the heat sink and the motor stator and is also secured into place via the fasteners. The tabbed end piece includes wire support tabs that provide strain relief to motor coil leads. The wire support tabs extend axially from circumferential locations of the tabbed end piece and include channels to guide the motor coil leads to solder contact points on the combined PCB.

RELATED APPLICATIONS

The present application claims priority to, and is a continuation of,U.S. Non-provisional patent application Ser. No. 16/422,337, filed May24, 2019, now U.S. Pat. No. 10,693,345, which claims priority to, and isa continuation of, U.S. Non-provisional patent application Ser. No.15/645,090, filed on Jul. 10, 2017, now U.S. Pat. No. 10,348,159, whichclaims priority to, and is a continuation of U.S. Non-provisional patentapplication Ser. No. 14/295,703, filed on Jun. 4, 2014, now U.S. Pat.No. 9,787,159, which claims priority to U.S. Provisional PatentApplication No. 61/832,012, filed on Jun. 6, 2013, the entire contentsof each of which are hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to brushless motor power tools.

BACKGROUND

Power tool motors can generally be grouped into two categories: brushedmotors and brushless motors. In a brushed motor, motor brushes make andbreak electrical connection to the motor due to rotation of the rotor.In a brushless motor power tool, such as power tool 100 of FIG. 1,switching elements are selectively enabled and disabled by controlsignals from a controller to selectively apply power from a power sourceto drive the brushless motor. The power tool 100 is a brushless hammerdrill having a housing 102 with a handle portion 104 and motor housingportion 106. The power tool 100 further includes an output unit 107,torque setting dial 108, forward/reverse selector 110, trigger 112,battery interface 114, and light 116.

FIG. 2 illustrates a simplified block diagram 120 of the brushless powertool 100, which includes a power source 122 (e.g., a battery pack),Field Effect Transistors (FETs) 124, a motor 126, hall sensors 128, amotor control unit 130, user input 132, and other components 133(battery pack fuel gauge, work lights (LEDs), current/voltage sensors,etc.). The Hall sensors 128 provide motor information feedback, such asmotor rotational position information, which can be used by the motorcontrol unit 130 to determine motor position, velocity, and/oracceleration. The motor control unit 130 receives user controls fromuser input 132, such as by depressing the trigger 112 or shifting theforward/reverse selector 110. In response to the motor informationfeedback and user controls, the motor control unit 130 transmits controlsignals to accurately control the FETs 124 to drive the motor 126. Byselectively enabling and disabling the FETs 124, power from the powersource 122 is selectively applied to the motor 126 to cause rotation ofa rotor. Although not shown, the motor control unit 130 and othercomponents of the power tool 100 are electrically coupled to the powersource 122 such that the power source 122 provides power thereto.

SUMMARY

In one embodiment, the invention provides a power tool including ahousing and a brushless direct current (DC) motor within the housing.The brushless DC motor includes a rotor and a stator, wherein the rotoris coupled to a motor shaft to produce a rotational output. The powertool further includes an annular metal end piece, a heat sink, and aprinted circuit board (PCB). The annular metal end piece is positionedat a first end of the brushless DC motor, while the heat sink ispositioned at a second end of the brushless DC motor opposite the firstend such that the brushless DC motor is between the heat sink and theannular metal end piece. The heat sink and the annular metal end pieceare secured together to clamp the brushless DC motor, thereby rigidlycoupling the heat sink to the brushless DC motor. The PCB is positionedat the second end of the brushless DC motor and is secured to the heatsink.

In another embodiment, the invention provides a power tool comprising:housing and a brushless direct current (DC) motor within the housing.The brushless DC motor includes a rotor and a stator, wherein the rotoris coupled to a motor shaft to produce a rotational output. The powertool further includes an annular metal end piece, a heat sink, threadedfastening elements, and a printed circuit board (PCB). The annular metalend piece is positioned at a first end of the brushless DC motor, whilethe heat sink is positioned at a second end of the brushless DC motoropposite the first end. The brushless DC motor is positioned between theheat sink and the annular metal end piece and has an axial length. Thethreaded fastening elements extend the axial length of the brushless DCmotor and secure the heat sink to the annular metal end piece. The PCBis positioned at the second end of the brushless DC motor and is securedto the heat sink. The PCB includes a Hall sensor, power switchingelements (e.g., field effect transistors), and a through-hole throughwhich the motor shaft extends.

In another embodiment, the invention provides a power tool including ahousing and a brushless direct current (DC) motor within the housing.The brushless DC motor includes a rotor and a stator, wherein the rotoris coupled to a motor shaft to produce a rotational output. The powertool further includes an annular metal end piece, an end cap, a heatsink, threaded fastening elements, and a printed circuit board (PCB).The annular metal end piece is positioned at a first end of thebrushless DC motor. The end cap is positioned over and secured to theannular metal end piece at the first end of the brushless DC motor. Theheat sink is positioned at a second end of the brushless DC motoropposite the first end such that the brushless DC motor is between theheat sink and the annular metal end piece. The heat sink and the annularmetal end piece are secured together to clamp the brushless DC motor,thereby rigidly coupling the heat sink to the brushless DC motor. Thebrushless DC motor has an axial length, and the threaded fasteningelements extend the axial length and secure the heat sink to the annularmetal end piece. The PCB is positioned at the second end of thebrushless DC motor and is secured to the heat sink. The PCB includes aHall sensor, power switching elements, and a through-hole through whichthe motor shaft extends.

Other aspects of the invention will become apparent by consideration ofthe detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a brushless power tool.

FIG. 2 illustrates a block diagram of a brushless power tool.

FIGS. 3A, 3B, and 4 provide additional views of the brushless power toolof FIG. 1.

FIG. 5 illustrates a Hall sensor board.

FIGS. 6-7 illustrate a brushless power tool having a combined surfboardPCB.

FIGS. 8A-C provide additional views of the combined surfboard PCB.

FIGS. 9-11 illustrate another brushless power tool having a combinedsurfboard PCB.

FIGS. 12-14 illustrate another brushless power tool having a combinedsurfboard PCB.

FIG. 15 illustrates a brushless power tool having a combined doughnutPCB.

FIGS. 16A-B show the combined doughnut PCB of the power tool of FIG. 15.

FIGS. 17A-B show a combined Hall and FET PCB of the power tool of FIG.15.

FIGS. 18A-B show a combined control PCB of the PCB stack.

FIGS. 19A-G illustrate a process for attaching a Hall and FET PCB andheat sink to a brushless motor.

FIG. 20 illustrates a wire wrap technique for a brushless motor.

FIG. 21 illustrates another combined Hall sensor and FET PCB for usewith a brushless power tool.

FIGS. 22A-C illustrate alternative locations for a control PCB on thebrushless power tool of FIG. 15.

FIGS. 23A-B illustrate an alternate brushless motor configuration.

FIGS. 24A-D illustrate components of the alternate brushless motorconfiguration of FIGS. 23A-B.

FIGS. 25A-B further illustrate components of the alternate brushlessmotor configuration of FIGS. 23A-B.

DETAILED DESCRIPTION

Before any embodiments of the invention are explained in detail, it isto be understood that the invention is not limited in its application tothe details of construction and the arrangement of components set forthin the following description or illustrated in the following drawings.The invention is capable of other embodiments and of being practiced orof being carried out in various ways.

FIG. 3A illustrates a cross section of the brushless power tool 100 ofFIG. 1, and FIG. 3B illustrates select components of the power tool 100.The power tool 100 includes separate printed circuit boards (PCBs) forvarious components of the power tool 100. More particularly, the powertool 100 includes a control printed circuit board (PCB) 136, a power PCB138, a forward/reverse PCB 140, a Hall sensor PCB 142, and alight-emitting diode (LED) PCB 144. Also illustrated in FIG. 3A is adrive mechanism 148 for transmitting the rotational output of the motor126 to the output unit 107, and a cooling fan 149 rotated by the motor126 and used to provide a cooling air flow over components of the powertool 100.

As shown in FIG. 4, the control PCB 136 is positioned at the base of thetool 100 between the handle portion 104 and the battery interface 114,which may also be referred to as a terminal block portion. The controlPCB 136 includes the motor control unit 130, which is operable toreceive user input, to receive motor information feedback, and tocontrol the FETs 124 to drive the motor 126. The control PCB 136 iselectrically and physically coupled to terminal blades 150. When abattery pack (i.e., the power source 122) is coupled to the batteryinterface 114, terminals of the battery pack are received by andelectrically coupled to the terminal blades 150. The number of terminalblades can vary based on the type of hand-held power tool. However, asan illustrative example, terminal blades 150 can include a batterypositive (“B+”) terminal, a battery negative (“B−”) terminal, a sense orcommunication terminal, and an identification terminal. As shown in FIG.4, the terminal blades 150 have tabs 152 that extend upward through thecontrol PCB 136. The tabs 152 may be directly soldered to the controlPCB 136, eliminating the need for additional power wires. The motorcontrol unit may use the communication terminal to communicate with abattery pack, allowing the battery pack to communicate whether it iscapable of discharging to the power tool 100 and other information.

The power PCB 138 includes the FETs 124, which are connected to andcontrolled by the motor control unit 130 of the control PCB 136. Asdiscussed above, the FETs 124 are also electrically coupled to the powersource 122 and the motor 126. In some embodiments, the FETs 124 aredirectly coupled (i.e., directly physically and/or thermally coupled) tothe heat sink 154 (e.g., directly on the heat sink, via copper tracingson the power PCB 138, etc.). In other embodiments, the FETs 124 are notdirectly coupled to the heat sink 154, but are in a heat transferrelationship with the heat sink 154.

The forward/reverse PCB 140 includes a forward/reverse switch that isoperated by the forward/reverse selector 110, which has three positions:forward, reverse, and neutral. The positions may be shifted between bymoving the forward/reverse selector/shuttle 110 in a direction normal tothe plane of the drawing of FIG. 1 (i.e., in/out of the page). When theforward/reverse selector 110 is shifted between these three positions,the selector 110 switches the forward/reverse switch of theforward/reverse PCB 140, which provides a signal to the motor controlunit 130. When the trigger 112 is depressed, the motor control unit 130causes the motor 126 to rotate clockwise, rotate counterclockwise, ornot rotate (e.g., in neutral) based on the position of the selector 110.

The Hall sensor PCB 142 includes hall sensors 128 to detect one or moreof the rotational position, velocity, and acceleration of the motor 126.The Hall sensor PCB 142 is electrically coupled to the control PCB 136to provide the outputs of the Hall sensors 128. As shown in FIGS. 3B and5, the Hall sensor PCB 142 includes a through-hole 156 through which amotor shaft/spindle 158 passes. Each Hall sensor 128 outputs a pulsewhen magnet of the rotor rotates across the face of that Hall sensor128. Based on the timing of the pulses from the Hall sensors 128, themotor control unit 130 can determine the position, velocity, andacceleration of the rotor. The motor control unit 130, in turn, uses themotor feedback information to control the FETs 124.

The light-emitting element (LED) PCB 144 includes the light 116, whichmay be a light emitting diode (LED). The LED PCB 144 is electricallycoupled to the control PCB 136 such that the motor control unit 130 isoperable to selectively enable and disable the light 116. The motorcontrol unit 130 may enable the light 116 when the trigger 112 isdepressed and/or when a separate light switch on the housing 102 isactivated by the user to selectively enable/disable the light 116independent of the trigger 112. The motor control unit 130 may furtherinclude a delay timer such that the light 116 remains illuminated for aperiod of time after the trigger 112 or light switch is depressed orreleased.

The motor control unit 130 is implemented by the control PCB 136, whichincludes motor control unit 130 includes combinations of hardware andsoftware that control operation of the power tool 100. For example, thecontrol PCB 136 includes, among other things, a processing unit (e.g., amicroprocessor, a microcontroller, or another suitable programmabledevice), a memory, input units, and output units. The processing unitincludes, among other things, a control unit, an arithmetic logic unit(“ALU”), and a plurality of registers, and is implemented using a knowncomputer architecture, such as a modified Harvard architecture, a vonNeumann architecture, etc. The processing unit, the memory, the inputunits, and the output units, as well as the various modules connected toor part of the control PCB 136 are connected by one or more controland/or data buses. In some embodiments, the control PCB 136 isimplemented partially or entirely on a semiconductor (e.g., afield-programmable gate array [“FPGA”] semiconductor) chip, such as achip developed through a register transfer level (“RTL”) design process.

The memory of the control PCB 136 includes, for example, a programstorage area and a data storage area. The program storage area and thedata storage area can include combinations of different types of memory,such as read-only memory (“ROM”), random access memory (“RAM”) (e.g.,dynamic RAM [“DRAM”], synchronous DRAM [“SDRAM”], etc.), electricallyerasable programmable read-only memory (“EEPROM”), flash memory, a harddisk, an SD card, or other suitable magnetic, optical, physical, orelectronic memory devices. The processing unit is connected to thememory and executes software instructions that are capable of beingstored in a RAM of the memory (e.g., during execution), a ROM of thememory (e.g., on a generally permanent basis), or another non-transitorycomputer readable medium such as another memory or a disc. Softwareincluded in the implementation of the battery pack can be stored in thememory of the controller. The software includes, for example, firmware,one or more applications, program data, filters, rules, one or moreprogram modules, and other executable instructions. The processing unitis configured to retrieve from memory and execute, among other things,instructions related to the control of the battery pack describedherein. The processing unit can also store various battery packparameters and characteristics (including battery pack nominal voltage,chemistry, battery cell characteristics, maximum allowed dischargecurrent, maximum allowed temperature, etc.). In other constructions, thecontrol PCB 136 includes additional, fewer, or different components.

The motor control unit 130 may further be in communication with one ormore sensors to monitor temperature, voltage, current, etc., of thepower tool 100 and an attached battery pack. The motor control unit 130may also include protection capabilities based on a variety of preset orcalculated fault condition values related to temperatures, currents,voltages, etc., associated with the operation of the hand-held powertool.

The various interconnections of the power tool 100 between the controlPCB 136, the power PCB 138, the forward/reverse PCB 140, the Hall sensorPCB 142, and the light-emitting element (LED) PCB 144 can lead to acomplex and space-consuming wiring layout within the housing 102.

FIGS. 6-7 illustrate a brushless power tool 200, which has similaritiesto power tool 100, but has a different electronics layout. The layout ofpower tool 200 has reduced wiring and assembly complexity relative tothe power tool 100. Additionally, the more compact and efficient layoutof the power tool 200 enables additional flexibility in design, such asby allowing different handle and body dimensions and shapes. Elements ofthe power tool 200 similar to those of the power tool 100 are similarlynumbered to simplify the description thereof.

Rather than a separate control PCB 136, power PCB 138, forward/reversePCB 140, and LED PCB 144, the power tool 200 includes a combinedsurfboard PCB 202 incorporating the functionality of each. The combinedsurfboard PCB 202 includes the FETs 124 of the power PCB 138, the light116 of the LED PCB 144, the motor control unit 130 of the control PCB136, and a forward/reverse switch 203 of the forward/reverse PCB 140(see FIG. 8C). Accordingly, in place of wires running through thehousing 102 to interconnect the various PCBs, the connections are madevia conductors on the combined surfboard PCB 202.

As illustrated, the combined surfboard PCB 202 has an elongated shape,with a length more than twice its width. The combined surfboard PCB 202has a rear portion adjacent to the motor 126 and a front portionadjacent to a trigger 112. The Hall sensor PCB 142 is positioned aboveand generally perpendicularly (i.e., within 15 degrees of aperpendicular) to the combined surfboard PCB 202).

Moreover, the combined surfboard PCB 202 is positioned near the fan 149,such that cooling air flow 204 passes over the FETs 124 and othercomponents of the combined surfboard PCB 202. The fan 149 operates todraw the cooling air flow 204 from the combined surfboard PCB 202towards the fan 149, or, as illustrated, to push the cooling air flow204 from the fan 149 over the combined surfboard PCB 202. Furthermore,air inlets and outlets are formed on the housing 102 to provide an inletand outlet path for the cooling air flow 204.

The components of the combined surfboard PCB 202 are exposed. In otherwords, the combined surfboard PCB 202 is not encapsulated or pottedwithin the housing 102 and is not protected against fluid within thehousing 102 from reaching the FETs 124 or motor control unit 130.Exposing the combined surfboard PCB 202 improves the thermal managementof the components thereon. For example, the cooling air flow 204 isoperable to reach and cool the FETs 124, enabling the FETs 124 tooperate at higher current levels and the motor 126 to operate at higherpower levels and generate higher torque for longer periods of time.

As shown in FIGS. 8A-C, the FETs 124 are mounted in a generally flatorientation on the combined surfboard PCB 202. In contrast, the FETs 124of the power tool 100 are mounted on the power PCB 138 in aperpendicular orientation. The combined surfboard PCB 202 also hasmounted thereon a heat sink 206 on a side opposite of the FETs 124 toprovide cooling of the FETs 124. The heat sink 206 is thermally coupledto the FETs 124 and includes heat sink fins 208 to improve the heatsinking capabilities of the heat sink 206. In some instances, one ormore additional heat sinks are positioned on the same side as the FETs124, such that the FETs 124 and the combined surfboard PCB 202 arelocated between the heat sink 206 and the one or more additional heatsinks. The one or more additional heat sinks are thermally coupled tothe FETs 124 to provide additional thermal management. A front portion209 of the bottom surface of the combined surfboard PCB 202 includes thelight 116 and the forward/reverse switch 203 mounted thereon. The FETs124 are mounted on a rear portion 210 of the bottom surface of thecombined surfboard PCB 202. The heat sink 206 is mounted on the rearportion 210 of the top surface of the combined surfboard PCB 202. TheHall sensor PCB 142 is above the surfboard PCB 202 and, taken together,generally form an upside-down “T” shape.

Additionally, the combined surfboard PCB 202 is centrally located withinthe power tool 200 above the trigger 112, but below the motor 126 anddrive mechanism 148. FIG. 7 illustrates a region 211 considered abovethe trigger 112 and below the motor 126. “Below the motor” does notrequire that the combined surfboard PCB 202 be directly below the motor126, but, rather, below a line extending parallel to the bottom surfaceof the motor 126. Accordingly, a shortened combined surfboard PCB 202that does not extend rearward in the tool 200 such that it is, in part,directly under the motor 126 as shown in FIG. 7 can still be considered“below the motor.” Similarly, “above the trigger” does not require thatthe combined surfboard PCB 202 be directly above the trigger, but,rather, within the region 211.

The central location allows relatively short wire connections betweenseveral components of the power tool 200. Furthermore, the exposed,unencapsulated nature of the combined surfboard PCB 202 further enablesmore flexibility in connection points to components thereon. That is,wires can reach components of the combined surfboard PCB 202 generallydirectly, rather than through limited ingress/egress ports of anencapsulation housing, allowing shorter and more direct wireconnections. More particularly, the combined surfboard PCB 202 is nearthe Hall sensor PCB 142, the light 116, the trigger 112, theforward/reverse switch 203, and terminals of the motor 126. Forinstance, FIG. 8A illustrates the short wires 212 connecting the Hallsensor PCB 142 and the combined surfboard PCB 202. The wires 212 may beflexible or rigid and are connected generally at a middle portion of thecombined surfboard PCB 202. Additionally, as shown, the wires 212 have alength less than a diameter of the motor 126, less than one-fourth ofthe length of the combined surfboard PCB 202, and less than a diameterof the Hall sensor PCB 142. Although a top surface of the combinedsurfboard PCB 202 is substantially parallel to the longitudinal axis ofthe motor shaft 158, the combined surfboard PCB 202 is angled slightlydownward with respect to the motor shaft 158 from the motor side to theoutput side of the power tool 200. As illustrated in FIG. 6-7, thecombined surfboard PCB 202 has a slight downward angle of less than 5degrees with respect to the motor shaft 158.

In some embodiments, the forward/reverse selector 110 includes a magnetmounted therein and the combined surfboard PCB 202 includes aforward/reverse Hall sensor (not shown) in place of the forward/reverseswitch 203. The forward/reverse Hall sensor detects movement of theembedded magnet when the forward/reverse selector 110 is moved, and asignal indicating the position or movement of the forward/reverseselector 110 is provided to the motor control unit 130.

The combined surfboard PCB 202 includes an exemplary component layout.In some embodiments, various components, such as one or more of the FETs124, are mounted on a different portion of the combined surfboard PCB202 (e.g., top instead of bottom surface, front instead of rear portion,etc.).

In some embodiments, the power tool 200 is a (non-hammer) drill/driverpower tool that includes a similar electronics layout, housing, motor,etc., but includes a different drive mechanism 148 having no hammermechanism.

FIGS. 9-11 illustrate a brushless impact wrench power tool 250 includingan impact output unit 252. The impact wrench is another type ofhand-held power tool used for generating rotational output, but includesan impact mechanism 254 that differs from the hammer-style drivemechanism 148 of the power tools 100 and 200.

The power tool 250 includes a similar layout as the power tool 200. Moreparticularly, the power tool 250 includes a housing 256 with a handleportion 258 and motor housing portion 260. The motor housing portion 260houses a motor 126 and is positioned above the handle portion 258. Thehandle portion 258 includes the battery interface 114 for coupling to abattery pack. Additionally, the power tool 250 includes the combinedsurfboard PCB 202 and Hall sensor PCB 142. The layout of power tool 250has reduced wiring and assembly complexity relative to the power tool100. Additionally, the more compact and efficient layout of the powertool 250 enables additional flexibility in design, such as by allowingdifferent handle and body dimensions and shapes. Elements of the powertool 250 similar to those of the power tools 100 and 250 are similarlynumbered to simplify the description thereof.

FIGS. 12-14 illustrate a brushless impact driver power tool 270including an impact output unit 272. The impact driver power tool 270 isanother type of hand-held power tool used for generating rotationaloutput that includes an impact mechanism 274 similar to the impactmechanism 254. Additionally, the power tool 270 includes a clip 276 forhanging the power tool 270 on various items, such as on a hook or toolbelt.

The power tool 270 includes a similar layout as the power tools 200 and250. More particularly, the power tool 270 includes a housing 278 with ahandle portion 280 and motor housing portion 282. The motor portion 282houses a motor 126 and is positioned above the handle portion 280. Thehandle portion 280 includes the battery interface 114 for coupling to abattery pack. Additionally, the power tool 270 includes the combinedsurfboard PCB 202 and Hall sensor PCB 142. The layout of power tool 270has reduced wiring and assembly complexity relative to the power tool100. Additionally, the more compact and efficient layout of the powertool 270 enables additional flexibility in design, such as by allowingdifferent handle and body dimensions and shapes. Elements of the powertool 270 similar to those of the power tools 100 and 270 are similarlynumbered to simplify the description thereof.

Although the physical layout of the combined surfboard PCB 202 may begenerally similar for each of the power tools 200, 250, and 270, theparticular software and hardware of the motor control unit 130 andratings of electrical components and FETs 124 may vary and be optimizedfor each tool.

FIG. 15 illustrates another brushless impact wrench power tool 300including the impact output unit 252 and impact mechanism 254, andhaving a battery pack 301 attached to the battery interface 114.Elements of the power tool 300 similar to the previously described powertools are similarly numbered to simplify the description thereof.

The layout of power tool 300, like that of the power tools 200, 250, and270, has reduced wiring complexity and reduced costs relative to thepower tool 100. However, the power tool 300 has a different PCB layoutin that the combined surfboard PCB 202 is not included. Rather, thecomponents of the combined surfboard PCB 202 are positioned on(generally) doughnut-shaped PCBs near the motor. Separate PCBs similarto the LED PCB 144 and forward/reverse PCB 140 may be provided in thepower tool 300 for inclusion and support of the light 116 and switch203, respectively.

More specifically, as shown in FIGS. 16A-B, the power tool 300 includesa Hall and FET PCB 302 and a control PCB 304 stacked on the motor 126and having a hole through which the motor shaft 158 passes. The Hall andFET PCB 302 is kept separated from the control PCB 304 by spacers 305(also referred to as standoffs). The Hall and FET PCB 302 includes theHall sensors 128 and the FETs 124, while the control PCB 304 includesthe motor control unit 130. Additionally, a heat sink 306, also with agenerally doughnut or ring shape, is secured between the Hall and FETPCB 302 and the motor 126. The heat sink 306 is generally used totransfer heat away from the FETs 124.

FIGS. 17A-B illustrate the Hall and FET PCB 302 in greater detail. TheHall and FET PCB 302 has a generally circular shape with a through-hole308 in the center. A motor shaft 158, as well as a motor bushing 309(see, e.g., FIG. 21), pass through the through-hole 308. The Hall andFET PCB 302 has two generally flat mounting surfaces: a first face 310(see FIG. 17A) and a second face 312 (see FIG. 17B). The FETs 124 aremounted on the Hall and FET PCB 302 in a flat orientation. Similarly,the control PCB 304 has a through-hole 314 and two generally flatmounting surfaces: a first face 316 (see FIG. 18A) and a second face 318(see FIG. 18B). The FETs 124 are shown mounted on the first face 310,while the Hall sensors 128 may be mounted on the second face 318,staggered at approximately 120 degrees, to be closer to the rotormagnets similar to the PCB 142 (see, e.g., FIG. 5). The control PCB 304further includes control PCB mounting holes 319. The control PCB 304 andHall and FET PCB 302 are located coaxially about the motor shaft 158 andthe faces 310, 312, 316, and 318 are generally parallel to each other.The PCBs 302 and 304 are secured to an end of the motor 126. By locatingFETs 124 with Hall sensors 128 on a single Hall and FET PCB 302 securedto the end of the motor 126, the Hall and FET PCB 302 is able to receivea large amount of air flow 204 for cooling in addition to reducing theinternal wiring of the power tool 300.

The Hall and FET PCB 302 further includes Hall and FET PCB mountingholes 320, motor lead pads 322, and copper bus bars 324. The copper busbars 324 allow for additional space on the Hall and FET PCB 302 to beused for other features such as high current traces. Accordingly, ratherthan occupying space on the Hall and FET PCB 302, the copper bus bars324 jump above the Hall and FET PCB 302. In alternative embodiments,traces on the Hall and FET PCB 302 are used instead of the copper busbars 324.

The Hall and FET PCB mounting holes 320 allow metal standoffs 305 (seeFIG. 16A-B) of the heat sink 306 to pass through the Hall and FET PCB302. The metal standoffs 305 provide spacing between the PCBs 302 and304 and allow the control PCB 304 to be attached to the heat sink 306.The metal standoffs 305 receive control PCB mounting screws insertedthrough mounting holes 319 of the control PCB 304 to secure the controlPCB 304 to the heat sink 306. In some embodiments, the control PCBmounting screws secure both the control PCB 304 and the Hall and FET PCB302 to the heat sink 306.

Furthermore, in some embodiments, Hall and FET PCB mounting holes 320may be used for both allowing metal standoffs 305 of the heat sink 306to pass through the Hall and FET PCB 302 and for securing the Hall andFET PCB 302 to the heat sink 306. Tightly securing the Hall and FET PCB302 to the heat sink 326 allows for heat to dissipate from the Hall andFET PCB 302 to the heat sink 306 more easily and minimizes vibrationbetween the Hall and FET PCB 302 and the motor 126. In other embodimentsof the invention, the number of mounting holes 319 and 320 and theirlocation on the PCBs 302 and 304 are varied. Furthermore, in otherembodiments, the general shape of the PCBs 302 and 304 is varied.

FIGS. 19A-G illustrate a process for attaching the motor 126, Hall andFET PCB 302, and heat sink 306 together. FIG. 19A illustrates a motorstator 330 of the motor 126 with plastic end caps 332 and 334 at eachend of the motor stator 330, respectively, and six motor leads 336 thatare stripped down to the plastic end cap 334. Wire support features 338are part of the plastic end cap 334 and will be used to properly guidethe motor leads 336, as explained below. FIG. 19B illustrates the heatsink 306 placed on the plastic end cap 334 of the motor stator 330. Themetal standoffs 305 of the heat sink 306 may be used for mounting thecontrol PCB 304 and/or locating the Hall and FET PCB 302 in someembodiments.

FIG. 19C illustrates the heat sink 306 fastened to the motor stator 330using heat sink mounting screws 340. Heat sink mounting clips 342 areattached to an end of the motor stator 330 opposite the end where theheat sink 306 is attached. The heat sink mounting screws 340 arethreadingly engaged with heat sink mounting standoffs of the heat sink306 and the heat sink mounting clips 342 to secure the heat sink 306 tothe motor stator 330. In some embodiments the number and location ofheat sink mounting elements are varied.

After securing the heat sink 306, the motor leads 336 are then bentdownward to fit within the wire support features 338 as shown in FIG.19D. Wrapping the motor leads 336 around the wire support features 338relieves strain on the motor leads 336 before they are soldered to theHall and FET PCB 302. In some embodiments, glue can also be applied tothe motor leads 336 to secure them to the heat sink 306.

FIG. 19E illustrates a heat sink pad 344 placed on top of the heat sink306. The heat sink pad 344 is a thin, electrical insulator with highthermal conductivity. These characteristics allow the heat sink pad 306to electrically isolate the metal heat sink 306 from the Hall and FETPCB 302 while still allowing heat from the Hall and FET PCB 302 todissipate via the heat sink 306.

FIG. 19F illustrates the Hall and FET PCB 302 placed on top of the heatsink pad 344 and heat sink 306. The motor leads 336 align with theopenings of the motor lead pads 322, and the metal standoffs 305 of theheat sink 306 pass through the Hall and FET PCB mounting holes 320. Toensure contact between the Hall and FET PCB 302 and the heat sink 306,downward force is applied to the Hall and FET PCB 302.

As illustrated in FIG. 19G, the motor leads 336 are soldered to themotor lead pads 322 to create solder joints 345, which not onlyelectrically connect the motor leads 336 to the Hall and FET PCB 302,but also mechanically attach the two components together. After creatingthe solder joints 345, the motor leads 336 are cut near the motor leadpads 322. As described above, in addition to the solder joints 345, theHall and FET PCB 302 can be secured to the heat sink 306 (which issecured to the motor 126) using Hall and FET PCB mounting screws.

After securing the Hall and FET PCB 302 to the motor 126 and heat sink306 combination, the control PCB 304 is then secured to the heat sink306 with the Hall and FET PCB 302 positioned between the heat sink 306and the control PCB 304. The control PCB 304 is secured to the heat sink306 using control PCB mounting screws received by the standoffs 305.

FIG. 20 illustrates the end of the motor stator 330 opposite from theend having the Hall and FET PCB 302. This view of the motor stator 330illustrates a wire crossover design, which wraps a wire behind theplastic end cap 332. Wrapping the wires of the motor stator 330 aroundthe plastic end cap 332 allows them to travel 180 degrees from one poleto the opposite pole of the motor stator 330 in an efficient manner. Thewrapped wires 346 are on top of a ledge portion 348, which wraps aroundthe motor stator 330, and are radially outside of tab portions 349 thatextend up from the ledge portion 348. As illustrated, at no point arethree wires located at the same circumferential position and stackedalong the ledge portion 348. Rather, at most, two wires are stacked,allowing a reduced height of the tab portions 349 and overall length ofthe motor stator 330.

In some embodiments, the control PCB 304 is not located adjacent to theHall and FET PCB 302 about the motor shaft 158, and the metal standoffs305 do not pass through the Hall and FET PCB 302. Rather, the length ofthe metal standoffs 305 is reduced such that they terminate at thesurface of the Hall and FET PCB 302. The reduced metal standoffs 305,which no longer provide spacing functionality, then receive Hall and FETPCB mounting screws to secure the Hall and FET PCB 302 to the heat sink306 and motor 126 combination, as shown in FIG. 21.

In embodiments in which the control PCB 304 is not located adjacent tothe Hall and FET PCB 302, the control PCB 304 may be referred to as thecontrol PCB 304 a. The control PCB 304 a may be located in severallocations within the power tool 300. The Hall and FET PCB 302 is coupledto the control PCB 304 a via cable connector 350 and a ribbon cable (notshown).

FIGS. 22A-C illustrate exemplary locations within the power tool 300that the control PCB 304 a may be positioned. In FIG. 22A, similar tothe power PCB 138 of the power tool 100, the control PCB 304 a islocated in the handle portion 258 of the power tool 300. In FIG. 22B,similar to the combined surfboard PCB 202, the control PCB 304 a islocated above the trigger 112 and handle portion 258, but below themotor 126 and impact mechanism 254. In FIG. 22C, similar to the controlPCB 136 of the power tool 100, the control PCB 304 a is located belowthe handle portion 258 and above the battery interface 114.

Although FIGS. 15-22 are described with respect to an impact wrenchpower tool 300, the various layout and motor assembly described may beimplemented in other types of power tools, such as a non-hammerdrill/driver power tool, a hammer drill/driver power tool (see, e.g.,FIGS. 1-9) and an impact driver power tool (see, e.g., FIGS. 12-14).

The above power tools (e.g., power tools 200, 250, 270, and 300) aredescribed as cordless, battery-powered tools. The battery packs, such asbattery pack 301, used to power these power tools may be, for instance,18 volt lithium ion type battery packs, although battery packs withother battery chemistries, shapes, voltage levels, etc. may be used inother embodiments. In some embodiments, these power tools are corded,AC-powered tools. For instance, in place of the battery interface 114and battery pack, the power tools include an AC power cord coupled to atransformer block to condition and transform the AC power for use by thecomponents of the power tools. These AC-powered tools may also includeone of the above-described layouts including one of the combinedsurfboard PCB layouts and doughnut PCB layouts.

FIGS. 23A and B illustrate an alternate brushless motor configuration399 that may be used in place of the configuration shown in, forinstance, FIGS. 15 and 22A-C. The brushless motor configuration 399includes a metal end piece 400 and a tabbed end piece 402 on oppositeends of the motor 126. The metal end piece 400 and tabbed end piece 402are more clearly illustrated in FIGS. 24C and 24A, respectively. Themetal end piece 400 and tabbed end piece 402 have a generally ring-likeshape. In the brushless motor configuration 399, the metal end piece 400is used in place of the plastic end cap 332 shown in FIG. 19A. Theplastic material of the plastic end cap 332 may be subject todeformation or movement at elevated temperatures when the motor 126 isin operation. The movement can include relative movement between the PCB302 and motor coils, which can lead to an increased risk of fracture toleads 336.

Use of the metal end piece 400 enables a rigid connection of the PCB 302to the motor 126. The metal end piece 400 and heat sink 306 includethrough-holes 404 and 405, respectively, for receipt of threadedfasteners 406, which secure the stator 330 and tabbed end piece 402therebetween. The threaded fasteners 406 may be thread-forming screws.The heat sink 306 is coupled to the metal end piece 400 via the threadedfasteners 406 to clamp the brushless DC motor between the heat sink 306and the metal end piece 400, thereby rigidly coupling the heat sink 306to the motor 126. The PCB 302 is rigidly coupled to the heat sink 306via screws 408; thus, rigidly coupling the heat sink 306 to thebrushless DC motor 126 rigidly couples the PCB 302 to the motor 126.

In some embodiments, the threaded fastener 406 is secured to the metalend piece 400 with a nut or the like. The motor configuration 399includes four through-holes 404 and fasteners 406 spread apart byapproximately 90 degrees along the circumference of the motor 126. ThePCB 302 is coupled to the heat sink 306 via six screws 408 spaced apartby approximately 60 degrees. The heat sink 306 is annular and includessix through-holes 410 for receiving screws 408, as shown in greaterdetail in FIG. 24D. The motor 126 has an axial length 409, and thethreaded fasteners 406 extend the axial length 409 along the outercircumference of the motor 126.

The brushless motor configuration 399 also includes the wire crossoverdesign as described with reference to FIG. 20. For instance, thebrushless motor configuration 399 includes an end cap 407 having theledge portion 348, tab portions 349, and wrapped wires 346. At no pointare more than two wires stacked at the same circumferential positionalong the ledge portion 348. The end cap 407 is more clearly illustratedin FIG. 24B and FIGS. 25A-B. The end cap 407 includes two locator tabs450 that are received in two respective recesses 452 of the metal endpiece 400. The locator tabs 450 each further include a snap tab 454extending over the outer circumference of the metal end piece 400 in theaxial direction of the motor 126, and then radially inward (i.e.,towards the motor shaft). The radially inward portion of the snap tab454 resides in a channel 456 on the outer circumference of the motor 126(see FIGS. 23A-B). The snap tab 454 flexes radially outward to allowaxial insertion of the metal end piece 400 into an annular recess 458 ofthe end cap 407. Once the metal end piece 400 is axially inserted, thesnap tab 454 returns to the radially inward position to securely couplethe end cap 407 to the metal end piece 400 (see FIG. 25A).

As shown in FIG. 24A, the tabbed end piece 402 (also referred to as asecond end cap) includes wire support tabs 412. The wire support tabs412 provide strain relief to reduce the stress on the leads 336 and,thereby, reduce the risk of damage or breakage of the leads 336. Theleads 336 are wrapped around the wire support tabs 412 before reachingthe soldering contact points (solder joints 345) on the PCB 302. Thewire support tabs 412 extend axially toward the PCB 302 from outercircumferential points of the tabbed end piece 402. The wire supporttabs 412 include channels 414 for receiving the leads 336. After passingthrough one of the channels 414, the lead 336 is bent at anapproximately ninety degree angle toward the soldering contact points onthe PCB 302 (see FIG. 23A). The motor configuration 399 includes threesets of wire support tabs 412, one tab 412 per lead 336, spread aroundthe tabbed end piece 402. The wire support tabs 412 are spaced apart byapproximately 120 degrees along the circumference of the tabbed endpiece 402.

Thus, the invention provides, among other things, a layout design andassembly of brushless power tools. Various features and advantages ofthe invention are set forth in the following claims.

What is claimed is:
 1. A power tool comprising: a housing; a brushlessdirect current (DC) motor within the housing, wherein the brushless DCmotor includes a rotor and a stator, wherein the rotor is coupled to amotor shaft arranged to rotate about a longitudinal axis, thelongitudinal axis extending through the motor shaft, and wherein themotor shaft is arranged to produce a rotational output to a drivemechanism; a metal end piece positioned at a first end of the brushlessDC motor; a heat sink positioned at a second end of the brushless DCmotor opposite the first end, wherein the brushless DC motor ispositioned between the heat sink and the metal end piece; threadedfastening elements securing the heat sink to the metal end piece,wherein the brushless DC motor has an axial length, and the threadedfastening elements extend the axial length of the brushless DC motorfrom the first end to the second end; and a printed circuit board (PCB)positioned at the second end of the brushless DC motor and secured tothe heat sink on a side of the heat sink that is opposite to thebrushless DC motor, wherein the PCB includes a Hall sensor, powerswitching elements, and a through-hole through which the longitudinalaxis extends, wherein the power switching elements are flat-mounted to asurface of the PCB that faces a direction opposite to the heat sink andthe brushless DC motor.
 2. The power tool of claim 1, wherein the metalend piece is annular.
 3. The power tool of claim 1, wherein the threadedfastening elements extend along an outer circumference of the brushlessDC motor.
 4. The power tool of claim 1, wherein the threaded fasteningelements are positioned in channels located in an outer surface of thebrushless DC motor.
 5. The power tool of claim 1, wherein the heat sinkincludes a second through-hole through which the longitudinal axisextends.
 6. The power tool of claim 1, further comprising an end cappositioned over the metal end piece at the first end of the brushless DCmotor.
 7. The power tool of claim 1, wherein the drive mechanism ispositioned at the second end of the brushless DC motor.
 8. A power toolcomprising: a housing; a brushless direct current (DC) motor within thehousing, wherein the brushless DC motor includes a rotor and a stator,wherein the rotor is coupled to a motor shaft arranged to rotate about alongitudinal axis, the longitudinal axis extending through the motorshaft, and wherein the motor shaft extends along an axial length of thebrushless DC motor to produce a rotational output; a metal end piecepositioned at a first end of the brushless DC motor; a heat sinkpositioned at a second end of the brushless DC motor opposite the firstend, wherein the brushless DC motor is positioned between the heat sinkand the metal end piece; fastening elements securing the heat sink tothe metal end piece, wherein the fastening elements extend along theaxial length of the brushless DC motor and bridge a gap between the heatsink and the metal end piece; and a printed circuit board (PCB)positioned at the second end of the brushless DC motor and secured tothe heat sink on a side of the heat sink that is opposite to thebrushless DC motor, wherein the PCB includes power switching elementsthat are flat-mounted to a surface of the PCB that faces a directionopposite to the heat sink and the brushless DC motor.
 9. The power toolof claim 8, wherein the PCB includes a Hall sensor and a firstthrough-hole through which the longitudinal axis extends; and whereinthe heat sink includes a second through-hole through which thelongitudinal axis extends.
 10. The power tool of claim 8, wherein thefastening elements extend along an outer circumference of the brushlessDC motor.
 11. The power tool of claim 8, wherein the fastening elementsare positioned in channels located in an outer surface of the brushlessDC motor.
 12. The power tool of claim 8, wherein the metal end piece isannular.
 13. The power tool of claim 8, further comprising an end cappositioned over the metal end piece at the first end of the brushless DCmotor.
 14. The power tool of claim 13, wherein the metal end pieceincludes a recess and the end cap includes a locator tab configured tofit in the recess and thereby align the end cap and the metal end piece.15. The power tool of claim 14, wherein the locator tab further includesa snap tab to secure the end cap to the metal end piece, the snap tabextending axially over the metal end piece then radially inward.
 16. Amotor assembly comprising: a brushless direct current (DC) motor withina housing, wherein the brushless DC motor includes a rotor and a stator,wherein the rotor is coupled to a motor shaft arranged to rotate about alongitudinal axis, the longitudinal axis extending through the motorshaft, and wherein the motor shaft extends along an axial length of thebrushless DC motor to produce a rotational output; a metal end piecepositioned at a first end of the brushless DC motor; a heat sinkpositioned at a second end of the brushless DC motor opposite the firstend, wherein the brushless DC motor is positioned between the heat sinkand the metal end piece; fastening elements securing the heat sink tothe metal end piece, wherein the fastening elements extend along theaxial length of the brushless DC motor and bridge a gap between the heatsink and the metal end piece; and a printed circuit board (PCB)positioned at the second end of the brushless DC motor and secured tothe heat sink on a side of the heat sink that is opposite to thebrushless DC motor, wherein the PCB includes power switching elementsthat are flat-mounted to a surface of the PCB that faces a directionopposite to the heat sink and the brushless DC motor.
 17. The motorassembly of claim 16, wherein the PCB includes a Hall sensor and a firstthrough-hole through which the longitudinal axis extends; and whereinthe heat sink includes a second through-hole through which thelongitudinal axis extends.
 18. The motor assembly of claim 16, whereinthe metal end piece is annular.
 19. The motor assembly of claim 16,further comprising an end cap positioned over the metal end piece at thefirst end of the brushless DC motor.
 20. The motor assembly of claim 16,wherein the fastening elements extend along an outer circumference ofthe brushless DC motor.